Small weapons simulators generally rely on pneumatic cylinder and piston arrangements installed in a weapon for simulating recoil action to enhance the "feel" of simulated firing exercises.
Prior art examples of small weapons simulators include the disclosure of U.S. Pat. No. 4,380,437 to Yarborough, featuring a recoil module based on a pneumatic cylinder and piston installed in a rifle butt. A valve actuated by a trigger allows compressed air to flow into the recoil module (piston), to provide an impulse simulating rifle firing, with live ammunition. The recoil module is a standard, manufactured unit for purchase.
A weapons trainer having a projection screen video system and a simulated weapon is disclosed in U.S. Pat. No. 5,035,622 to Marshall et al, featuring recoil of the simulated weapon provided by pneumatics.
In prior art weapons simulators, the air piston is used to push and pull the bolt mechanism. Since the air piston must release trapped air, its motion is slower than the gun mechanism itself, and thus the recoil feeling is not realistic. A pneumatic trigger mechanism is often used, and this is not a faithful simulation of a real trigger. No "click" is heard, or the hammer is generally eliminated, so the real "feel" of a weapon is absent. Usually some mechanical elements in the trigger mechanism are eliminated or modified.
In addition, the difficulty associated with repairing simulated weapons which utilize a pneumatic cylinder is due to the need to remove the cylinder, which is a time consuming process. Many air connections are needed in these designs, since the air flow is directed to provide two-directional rifle bolt movement, and these air connections complicate the breakdown and re-assembly procedure, making for costly maintenance and repair.
Thus, it would be desirable to provide recoil simulation without installing an external air cylinder for recoil.